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psql invalid command \N while restore sql
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Can happen when e.g. create table... fails in the start, but loading continues.
– JaakL
Jan 11 '17 at 11:34
1
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Python __call__ special method practical example
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This example uses memoization, basically storing values in a table (dictionary in this case) so you can look them up later instead of recalculating them.
Here we use a simple class with a __call__ method to calculate factorials (through a callable object) instead of a factorial functi...
How to add “on delete cascade” constraints?
...ible to add ON DELETE CASCADES to the both foreign keys in the following table without dropping the latter?
3 Answers
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Insert picture/table in R Markdown [closed]
So I want to insert a table AND a picture into R Markdown. In regular word document I can just easily insert a table (5 rows by 2 columns), and for the picture just copy and paste.
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What are the underlying data structures used for Redis?
...e implemented with linked lists.
Sets and Hashes are implemented with hash tables.
Sorted sets are implemented with skip lists (a peculiar type of balanced trees).
But when lists, sets, and sorted sets are small in number of items and size of the largest values, a different, much more compact enco...
MySQL load NULL values from CSV data
... up containing an empty string:
LOAD DATA INFILE '/tmp/testdata.txt'
INTO TABLE moo
FIELDS TERMINATED BY ","
LINES TERMINATED BY "\n"
(one, two, three, @vfour, five)
SET four = NULLIF(@vfour,'')
;
If they're all possibly empty, then you'd read them all into variables and have multiple SET stateme...
What do the terms “CPU bound” and “I/O bound” mean?
... 363.64 166.67 2.18
MARK RESULTS TABLE
Mark Name MultiCore SingleCore Scaling
----------------------------------------------- ---------- ---------- ----------
CoreMark-PRO 18743....
How to “perfectly” override a dict?
... the minimal version that shuts the ABC up.
from collections.abc import MutableMapping
class TransformedDict(MutableMapping):
"""A dictionary that applies an arbitrary key-altering
function before accessing the keys"""
def __init__(self, *args, **kwargs):
self.store = dict...
Repeat each row of data.frame the number of times specified in a column
...ndRows(df, "freq")
Simple syntax, very fast, works on data.frame or data.table.
Result:
var1 var2
1 a d
2 b e
2.1 b e
3 c f
3.1 c f
3.2 c f
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Rails: Adding an index after adding column
Suppose I created a table table in a Rails app. Some time later, I add a column running:
5 Answers
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